Former 49ers quarterback Alex Smith, who rejuvenated his career with Kansas City last season, agreed to a four-year, $68 million extension with the team Sunday.

Smith, who is due $7.5 million this season, will receive $45 million in new guarantees.

After the 49ers traded Smith to Kansas City for a two second-round draft picks, he had possibly the best season of his career.

He threw for a career-high 3,313 yards and 23 touchdowns against only seven interceptions, even while skipping a meaningless regular-season finale.

"It was a priority of ours to get this deal done and keep Alex in a Chiefs uniform long term," Chiefs general manager John Dorsey said in a statement. "Alex is a proven leader on and off the field. He is a special individual with a lot of ability, and we are fortunate to have him here."

Sam a free agent: Defensive end Michael Sam, the first openly gay athlete ever drafted by an NFL team, cleared waivers after being released Saturday by the St. Louis Rams and became a free agent.

The Rams appeared unlikely to re-sign Sam to the practice squad because the defensive line is a team strength.

"It's the strength of our team," head coach Jeff Fisher said, adding that the nine defensive linemen on the roster are a "significant number."

Mayowa, an undrafted free agent out of Idaho in 2013, played two games for Seattle last season. The 6-foot-3, 252-pound lineman had three solo tackles, including two behind the line of scrimmage, against the Raiders in the preseason finale Thursday.

The team said it won't announce its practice squad until Monday afternoon. Various reports have the Raiders agreeing to deals with guard Lamar Mady, tight end Scott Simonson and defensive lineman Ricky Lumpkin.

In Houston, Mallett will move into the backup role created when the Texans cut Case Keenum on Sunday. Keenum had been competing with rookie fourth-round pick Tom Savage for the No. 2 role behind Ryan Fitzpatrick.

Other moves: Cleveland released Rex Grossman, leaving starter Brian Hoyer and rookie backup Johnny Manziel as the only quarterbacks on the roster. ... Atlanta claimed former Raiders and 49ers linebacker Nate Stupar, who was waived by Jacksonville on Saturday. ... Miami claimed safety Brandian Ross, who spent the past two seasons with Oakland.